It is known that a discotic liquid-crystal compound, especially a liquid-crystal compound capable of expressing a discotic nematic phase (hereinafter referred to as “ND phase”) is an extremely important compound as a material for optical compensatory films. Typical examples of a liquid-crystal compound are, for example, benzene derivatives, triphenylene derivatives, toluxene derivatives, phthalocyanine derivatives, as in a report by Destrade, et al. (see Molecular Crystals and Liquid Crystals, 1981, Vol. 71, p. 111), in which, in general, any of these derivatives forms a center mother nucleus of the molecule thereof and is substituted with radial side branches of a linear alkyl or alkoxy group or a substituted benzoyloxy group.
However, there are reported only limited cases relating to a liquid-crystal compound capable of expressing an ND phase (see THE CHEMICAL RECORD, 2002, Vol. 2, p. 59). For example, 2,3,6,7,10,11-hexa{4-(4-acryloyloxyhexyloxy)-benzoyloxy}triphenylene capable of expressing an ND phase within a broad temperature range is disclosed, and this has a mother nucleus of triphenylene that is substituted with 6 side branches. Almost all the other compounds are substituted with radial 6 side branches.
These days it is reported that a benzene compound, in which the benzene ring is substituted with three 1,3,4-oxadiazole substituents at the 1-, 3- and 5-positions thereof, expresses an ND phase (see Molecular Crystals and Liquid Crystals, 2001, Vol. 370, p. 391). However, no one knows a compound having less than 3 side branches and capable of expressing an ND phase.
As in the above, it has heretofore been considered that a compound having a larger number of side branches is more advantageous for expressing a discotic nematic phase.
A liquid-crystal compound capable of expressing an ND phase is useful, but has some problems in that conventional discotic liquid-crystal compounds have complicated structures and are difficult to produce and their costs are high.